Bone Cancer
Detailed
Guide: Bone Cancer
Do We Know What Causes Bone Cancer?
The
exact cause of most bone cancers is not known. However,
scientists have found that bone cancers are associated with
a number of other conditions, which are described in the
section on risk factors. Keep in mind that most people with
bone cancers do not have any known risk factors and that
the causes of their cancers remain unknown at this time.
Research is underway to learn more about these causes.
During
the past few years, scientists have made great progress
in understanding how certain changes in a person's DNA can
cause bone cells to become cancerous. DNA carries the instructions
for nearly everything our cells do. We usually look like
our parents because they are the source of our DNA. However,
DNA affects more than our outward appearance. It may influence
our risks for developing certain diseases, including some
kinds of cancer.
Some
genes (parts of our DNA) contain instructions for controlling
when our cells grow and divide. Genes that promote cell
division are called oncogenes. Others that slow down cell
division or cause cells to die at the right time are called
tumor suppressor genes. Cancers can be caused by DNA mutations
(defects) that activate oncogenes or inactivate tumor suppressor
genes. Some people with cancer have DNA mutations that they
inherited from a parent. These mutations increase their
risk for the disease. Usually, however, DNA mutations are
acquired during life rather than inherited before birth.
The
DNA mutations that cause some inherited forms of bone cancers
are known. The Li-Fraumeni syndrome is caused by inherited
mutations that inactivate the p53 tumor suppressor gene.
This results in a very high risk of developing one or more
types of cancer that include breast cancer, brain cancer,
osteosarcoma, and other sarcomas. Inherited defects of the
Rb tumor suppressor gene increase the risk of developing
retinoblastoma, a type of eye cancer that affects children.
Children with this defect also have an increased risk for
developing osteosarcoma.
When
children inherit Rb or p53 mutations from a parent, these
mutations are present in every cell of their body and, therefore,
can be detected by testing DNA of blood cells. Because every
person has two p53 and two Rb genes but passes only one
of each to their children (the other gene comes from their
mate), the odds that a parent will pass their mutated gene
on to a child are 1 out of 2.
The
majority of bone cancers are not caused by inherited DNA
mutations. They are the result of mutations acquired during
the person's lifetime. These mutations are present only
in the cancer cells and are not passed on to the patient's
children. Although radiation is very useful in treating
some forms of cancer, it can also cause cancer by damaging
DNA. This is why bones exposed to radiation as a treatment
for other cancers are more likely to develop bone cancer
later in the patient's lifetime.
Other
DNA mutations have no apparent cause but may result from
random errors that occur when cells reproduce. Before a
cell divides, it must copy its DNA so that both new cells
have the same set of instructions. Sometimes this copying
process is not completely accurate. Scientists still do
not know exactly why or how these mutations happen to some
people but not to others.
Fortunately,
cells have ways of "proofreading" DNA copies and
repairing any errors. But when cells divide shortly after
their DNA is damaged, new "daughter cells" may
be formed before the original cell has time to repair its
DNA damage. Once the cells are formed, it is too late to
repair the damage. The result is that cell instructions
for growth control can be permanently altered, and a cancer
(such as osteosarcoma) may develop. This is why normal situations
(such as the teenage growth spurt) and diseases (such as
Paget disease of bone, multiple exostoses, and multiple
osteochondromas) causing rapid bone growth increase the
risk of developing osteosarcoma.
Although
scientists are making progress in understanding this process,
there are still some points that are not completely understood.
As their knowledge increases, they hope to develop ways
to better prevent and treat bone cancers.
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The information on this page has been extracted from
http://www.cancer.org/docroot/CRI/content/
CRI_2_4_2X_Do_we_know_what_causes_bone_cancer_2.asp?sitearea=.
